Triangle of Safety
The triangle of safety is bordered by the anterior axillary line (pectoralis major) and posterior axillary line (latissimus dorsi) and the 5th intercostal space (roughly the level of the nipple in a thin male). The only muscles you need to go through are the serratus anterior and intercostals. The only structure of significance is the long thoracic nerve. If injured it will produce a winged scapula. This is rare. This the first choice for chest tube insertion in trauma.